It is increasingly common for people to use client-side devices to communicate via a radio access network (RAN) with other devices, whether those devices are directly connected to the same RAN or to another network (such as another RAN or a transport network, as examples) to which that RAN directly or indirectly provides access. These client-side devices are generally referred to herein as access terminals, though this term is intended to broadly encompass devices known as mobile stations, mobile devices, user equipment, wireless-communication devices, cellphones, smartphones, personal digital assistants (PDAs), tablets, laptops, air cards, Universal Serial Bus (USB) dongles, and/or any other device or combination of devices capable of functioning as an access terminal according to this disclosure.
Typically, the wireless communications that are sent from the RAN to one or more access terminals are described as being sent on the “forward link,” while those wireless communications that are sent from one or more access terminals to the RAN are described as being sent on the “reverse link.” These communications are typically formatted in accordance with a wireless-communication protocol, one example type of which is known as code division multiple access (CDMA). Moreover, CDMA networks that operate according to industry specifications (IS) such as IS-95 and IS-2000 are often referred to as 1×RTT (or just “1×”) networks, where 1×RTT stands for “Single Carrier Radio Transmission Technology.”
Furthermore, some RANs operate according to a particular type of CDMA protocol known as EV-DO (“Evolution Data Optimized”). These RANs are generally configured to operate according to one or more versions of IS-856, and are designed to provide high-rate packet-data service, including Voice over Internet Protocol (IP) (VoIP) service, to access terminals using a technique that is known as time-division multiplexing (TDM) on the forward link and what is essentially 1×-CDMA technology on the reverse link.
More generally, RANs can be configured to operate according to any of numerous other wireless-communication protocols, some examples of which are Wi-Fi (IEEE 802.11), WiMAX (IEEE 802.16), Long Term Evolution (LTE), time division multiple access (TDMA), Global System for Mobile Communications (GSM), and the like.
In RANs that are of a type often known as wireless wide area networks (WWANs) (or cellular wireless networks), the entities with which access terminals communicate over the air interface are known by terms such as “base stations” and “access nodes,” among others. These terms are sometimes used in different ways to refer to different entities. For example, the term “base station” is sometimes used to describe simply a device known as a base transceiver station (BTS), which contains the hardware, antennas, and so forth that actually conduct the over-the-air portion of the communication with the access terminals on behalf of the RAN. At times, however, the term “base station” or “access node” is used to refer to a combination of (i) one or more BTSs and (ii) a device known as a “base station controller” (BSC) (or “radio network controller” (RNC)), which controls the BTS(s) and connects it (them) to the rest of the network. In a typical scenario, an access terminal registers with a RAN via a particular BTS, and then operates in what is known as “idle mode” on a carrier frequency in a coverage area (e.g., a sector) provided by that BTS. If the access terminal is attempted to be contacted by another device, the RAN will typically page the access terminal via at least that particular BTS. The access terminal would typically respond by requesting and establishing communication on what is known as an air-interface traffic channel (or simply a “traffic channel”), and then conduct the relevant communication. In other instances, the access terminal is the initiator, in which case the access terminal typically sends the RAN an access-request message in order to request and establish communication on a traffic channel and then conduct the relevant communication.